================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff8881124f5590 by task syz.5.1968/7062 CPU: 0 PID: 7062 Comm: syz.5.1968 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:77 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:435 [inline] kasan_report+0x100/0x140 mm/kasan/report.c:452 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 rcu_do_batch+0x448/0xaf0 kernel/rcu/tree.c:2484 rcu_core+0x50a/0xca0 kernel/rcu/tree.c:2735 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748 __do_softirq+0x255/0x563 kernel/softirq.c:309 asm_call_irq_on_stack+0xf/0x20 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline] do_softirq_own_stack+0x60/0x80 arch/x86/kernel/irq_64.c:77 invoke_softirq kernel/softirq.c:405 [inline] __irq_exit_rcu+0x128/0x150 kernel/softirq.c:435 irq_exit_rcu+0x9/0x10 kernel/softirq.c:447 sysvec_apic_timer_interrupt+0xbf/0xe0 arch/x86/kernel/apic/apic.c:1106 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635 RIP: 0010:__pte_map_lock_speculative+0x2bf/0x710 mm/memory.c:2758 Code: 8b 7d c0 4c 8b 65 08 43 80 3c 2e 00 74 08 4c 89 ff e8 e5 b0 09 00 4d 8b 37 0f 1f 44 00 00 e8 48 3b cf ff 31 c0 fb 48 83 c4 38 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 4c 8b 65 08 43 80 3c 2e 00 74 08 RSP: 0000:ffffc90001c8fb30 EFLAGS: 00000296 RAX: 1ffff92000391f01 RBX: ffff888111c43318 RCX: ffff88812bde2780 RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffffc90001c8fd20 RBP: ffffc90001c8fb58 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff52000391f50 R12: ffffea00044710e8 R13: 0000000000000002 R14: dffffc0000000000 R15: ffffc90001c8fd28 pte_map_lock mm/memory.c:2769 [inline] do_anonymous_page mm/memory.c:3935 [inline] handle_pte_fault+0x1a9c/0x3910 mm/memory.c:4795 ___handle_speculative_fault mm/memory.c:5228 [inline] __handle_speculative_fault+0xe77/0x1390 mm/memory.c:5277 handle_speculative_fault include/linux/mm.h:1849 [inline] do_user_addr_fault+0x846/0xe20 arch/x86/mm/fault.c:1266 handle_page_fault arch/x86/mm/fault.c:1436 [inline] exc_page_fault+0x5a/0xc0 arch/x86/mm/fault.c:1492 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:571 RIP: 0033:0x7f79847a224e Code: c1 49 39 4f 08 72 54 8d 4d ff 85 ed 74 3b 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 39 f0 72 1b 4d 8b 07 49 89 c1 49 29 f1 <47> 0f b6 0c 08 45 84 c9 74 08 45 88 0c 00 49 8b 47 10 48 83 c0 01 RSP: 002b:00007f7983343470 EFLAGS: 00010206 RAX: 000000000153f001 RBX: 00007f7983343530 RCX: 000000000000004f RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00007f79833435d0 RBP: 0000000000000102 R08: 00007f797af24000 R09: 000000000153f000 R10: 0000000000000000 R11: 00007f7983343540 R12: 0000000000000001 R13: 00007f79849a2000 R14: 0000000000000000 R15: 00007f79833435d0 Allocated by task 7060: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track mm/kasan/common.c:45 [inline] set_alloc_info mm/kasan/common.c:430 [inline] ____kasan_kmalloc mm/kasan/common.c:509 [inline] __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518 kasan_kmalloc include/linux/kasan.h:254 [inline] __kmalloc+0x19f/0x330 mm/slub.c:4038 kmalloc include/linux/slab.h:560 [inline] kzalloc include/linux/slab.h:667 [inline] l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772 __sys_connect_file net/socket.c:1867 [inline] __sys_connect+0x3ce/0x450 net/socket.c:1884 __do_sys_connect net/socket.c:1894 [inline] __se_sys_connect net/socket.c:1891 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1891 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Freed by task 112: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track+0x4a/0x70 mm/kasan/common.c:45 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370 kasan_slab_free include/linux/kasan.h:220 [inline] slab_free_hook mm/slub.c:1600 [inline] slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626 slab_free mm/slub.c:3208 [inline] kfree+0xc0/0x270 mm/slub.c:4196 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline] l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447 kthread+0x324/0x3b0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 Last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358 __call_rcu kernel/rcu/tree.c:2980 [inline] call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447 __sock_release net/socket.c:597 [inline] sock_close+0xb8/0x200 net/socket.c:1287 __fput+0x2dc/0x730 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x61/0xcb The buggy address belongs to the object at ffff8881124f5400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff8881124f5400, ffff8881124f5600) The buggy address belongs to the page: page:ffffea0004493d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1124f4 head:ffffea0004493d00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 106, ts 6150661135, free_ts 0 set_page_owner include/linux/page_owner.h:35 [inline] post_alloc_hook mm/page_alloc.c:2456 [inline] prep_new_page+0x176/0x190 mm/page_alloc.c:2462 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1813 [inline] new_slab+0x84/0x3f0 mm/slub.c:1874 new_slab_objects mm/slub.c:2632 [inline] ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796 __slab_alloc+0x63/0xa0 mm/slub.c:2836 slab_alloc_node mm/slub.c:2918 [inline] slab_alloc mm/slub.c:2960 [inline] __kmalloc_track_caller+0x1e4/0x310 mm/slub.c:4541 __kmalloc_reserve net/core/skbuff.c:144 [inline] __alloc_skb+0xdc/0x520 net/core/skbuff.c:212 alloc_skb include/linux/skbuff.h:1126 [inline] alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x335/0x5a0 lib/kobject_uevent.c:409 kobject_uevent_env+0x52b/0x700 lib/kobject_uevent.c:608 kobject_synth_uevent+0x452/0x940 lib/kobject_uevent.c:208 uevent_store+0x25/0x60 drivers/base/core.c:2320 dev_attr_store+0x5e/0x80 drivers/base/core.c:2018 sysfs_kf_write+0x129/0x150 fs/sysfs/file.c:143 kernfs_fop_write_iter+0x2bd/0x400 fs/kernfs/file.c:296 page_owner free stack trace missing Memory state around the buggy address: ffff8881124f5480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881124f5500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881124f5580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881124f5600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881124f5680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ip6_tunnel: syztnl2 xmit: Local address not yet configured! ---------------- Code disassembly (best guess): 0: 8b 7d c0 mov -0x40(%rbp),%edi 3: 4c 8b 65 08 mov 0x8(%rbp),%r12 7: 43 80 3c 2e 00 cmpb $0x0,(%r14,%r13,1) c: 74 08 je 0x16 e: 4c 89 ff mov %r15,%rdi 11: e8 e5 b0 09 00 call 0x9b0fb 16: 4d 8b 37 mov (%r15),%r14 19: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 1e: e8 48 3b cf ff call 0xffcf3b6b 23: 31 c0 xor %eax,%eax 25: fb sti 26: 48 83 c4 38 add $0x38,%rsp * 2a: 5b pop %rbx <-- trapping instruction 2b: 41 5c pop %r12 2d: 41 5d pop %r13 2f: 41 5e pop %r14 31: 41 5f pop %r15 33: 5d pop %rbp 34: c3 ret 35: 4c 8b 65 08 mov 0x8(%rbp),%r12 39: 43 80 3c 2e 00 cmpb $0x0,(%r14,%r13,1) 3e: 74 08 je 0x48